Surface and dust features seen on the nucleus of comet Halley

P/Halley, the Model Comet, in View of the Imaging Experiment Aboard the Vega Spacecraft

“…So it came somewhat as a surprise when both the VEGA and Giotto imaging teams pointed out that the brightness distribution along the jet cores close to the nucleus deviates from the expected 1/r behavior (Toth et al, 1987;Thomas and Keller, 1987). The VEGA team, knowing exactly the spatial orientation of jets, were able to identify a 30-to 40-km range from the nucleus where the deviation is pronounced (Szego et al, 1988) for several prominent jet features. Though unable to do spatial reconstruction, the Giotto team concluded that this deviation also occurs within the first 10 km (Thomas et al, 1988).…”

“…Thomas et al (1988) concluded that this effect gives the major influence on intensity profiles. This view was challenged by Szego et al (1988), based on the results of Huebner et al (1988), pointing out that the geometrical overlap operates only much closer to the surface if a reasonable source extension (1.5 km) and jet opening angle (10° ) are considered. Szego et al (1988) provided an alternative explanation based on grain fragmentation.…”